Preheat your oven to 350°F (175°C). Place the butter in a 9x13 baking dish and let it melt in the oven while it preheats.
In a mixing bowl, whisk together the flour, sugar, baking powder, and salt. Slowly pour in the milk and mix until smooth.
Once the butter has melted, carefully pour the batter over it. Do not stir. Just let the magic happen.
Spoon the peaches (syrup and all) evenly over the batter. Again, don’t stir!
Sprinkle ground cinnamon generously over the top.
Bake for about 40 minutes, or until the top is golden brown and bubbly.
Serve warm with a scoop of vanilla ice cream if you're feeling fancy (and you should be).